Traveling electromagnetic waves on linear metallic nanosphere arrays

In a recent report [1] we have employed the source scattering-matrix formulation [2] with vector spherical wave functions [3]–[4] to investigate traveling electromagnetic waves on infinite linear periodic arrays of lossless penetrable (magnetodielectric) spheres. It is assumed that either the spheres are sufficiently small that only the dipole scattered fields can be excited, or the frequency is such that all the scattered multipole fields are negligible except the dipole fields. Accordingly, the sphere scattering is treated using only electric and magnetic dipole vector spherical waves, the dipoles being orthogonal to each other and to the array axis. A summary of this work was presented at a recent conference [5]. Although our investigation was motivated in part by the recent theoretical demonstration by Holloway et al. [6] that a doubly negative medium can be formed by embedding an array of magnetodielectric spheres in a background matrix, the results are equally applicable to arrays of lossless “metallic” spheres, with negative relative permittivity and with relative permeability equal to one, excited by an electromagnetic field transverse to the array axis.